According to a new study, a Toyota Prius hybrid, like this one turning onto Market Street in S.F., has a similar carbon footprint to an electric car in Texas, a state that generates much of its electricity from coal. less

According to a new study, a Toyota Prius hybrid, like this one turning onto Market Street in S.F., has a similar carbon footprint to an electric car in Texas, a state that generates much of its electricity from ... more

Photo: Michael Macor, The Chronicle

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A Nissan Leaf, shown at left recharging at North Bay Nissan in Petaluma, is significantly more expensive than the comparably sized Nissan Versa, which runs on gasoline, even with state and federal incentives.

A Nissan Leaf, shown at left recharging at North Bay Nissan in Petaluma, is significantly more expensive than the comparably sized Nissan Versa, which runs on gasoline, even with state and federal incentives.

As a result, they are far greener in some parts of the country than in others, according to a report issued Monday by the Union of Concerned Scientists.

In California - which derives most of its electricity from natural gas plants, nuclear reactors, renewable power sources and hydroelectric dams - an electric car produces the same amount of global warming emissions as a gasoline-burning car that gets 79 miles to the gallon.

In Texas, which is more dependent on coal, an electric car has the same greenhouse gas footprint as a gas-powered car getting 46 miles per gallon - about the same as a Toyota Prius hybrid.

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And in several coal-centric states, an electric car actually produces more emissions than a hybrid. Even there, however, the electric will still outperform the standard compact car. The benefit is not as great as it could be, but it is there.

"For people who might have had doubts about the climate benefits of electric vehicles, this analysis shows they're positive, no matter where you live," said report author Don Anair with the union, which is a science-based advocacy group.

Key consumer details

Geared toward consumers, the report tries to give potential buyers two key pieces of information about the plug-in cars that are slowly proliferating on American roads. In addition to the vehicles' environmental benefits, the authors examine how much money drivers can save each year by ditching the gas pump and plugging in instead.

Again, location makes all the difference.

In San Francisco, drivers can save $1,140 on fuel per year, assuming they switch to a special electricity rate that utility Pacific Gas and Electric Co. offers to electric car owners. In Houston, drivers served by the TXU Energy utility can save $1,000 by recharging rather than filling up.

To make those calculations, the union's researchers examined the electricity rates in each specific city and assumed a gasoline price of $3.50 per gallon. Nationwide, the amount drivers can save ranges from $750 to $1,200. The savings could add up to nearly $13,000 over the life of the car.

In many cases, those savings would not make up for the higher sticker price that buyers currently pay for electric cars. The Nissan Leaf, for example, has a suggested retail price of $35,200, and in California, incentives from the state and federal governments can bring the price down to $25,200. That's still substantially more than a comparably sized Nissan Versa, which has a suggested retail price ranging from $10,990 to $18,490.

"They've got a ways to go, pricing and otherwise, before they can convince the bulk of Americans that this is something you ought to put in your garage," said John O'Dell, senior editor with the Edmunds.com auto information website.

Shield from gas prices

Electric car advocates, however, compare paying the higher up-front cost to buying an insurance policy. Although electricity rates are likely to rise over time, gasoline prices will probably climb more, they say. Meanwhile, the cost of electric cars will fall as production ramps up.

And O'Dell, who drives a Leaf, says the union's report does not include all the potential savings electric car drivers may see, because the vehicles require less maintenance than their gas-burning counterparts.

"You have to rotate your tires, you have to change your windshield wipers and your wiper fluid, and that's about it," he said. "There's nothing to lube anymore."

Many electric car buyers, so far, have been motivated primarily by environmental concerns, seeing the vehicles as a way to combat global warming one vehicle at a time. Anair and his fellow researchers tried to quantify the cars' global warming benefits using an approach called "well to wheels," which examines the greenhouse gas emissions associated with producing a particular energy source.

For gasoline, they looked at the emissions produced by pumping crude oil from the ground, shipping it to refineries, processing it into gasoline and burning the gas while driving. For electricity from coal-fired plants, they examined the greenhouse gases produced by mining coal, transporting it to power plants and burning it. Each energy source received the same treatment.

Changing emissions

The emissions generated by electric cars will probably change in the coming years.

A dramatic drop in natural gas prices has prompted some utilities to ditch plans for new coal-fired power plants, a trend that analysts expect to accelerate. Power plants that use natural gas produce far fewer greenhouse gas emissions than plants that burn coal. Meanwhile, the amount of electricity generated each year by renewable power sources is growing.

"As the electricity grid improves," Anair said, "EVs will become cleaner over time."